Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-11-09
2003-12-02
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S109400, C430S111400
Reexamination Certificate
active
06656655
ABSTRACT:
RELATED APPLICAITON
The present invention is based on Japanese Patent Application No. 2000-357657, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toner for developing an electrostatic latent image to be used in printers and copiers that employ electrophotographic method, electrostatic printing method or the like.
2. Description of the Related Art
In full color image forming apparatuses, generally, part of a toner image is moved to a fixing member during fixing, and a release oil is applied to the fixing member to prevent offset phenomenon soiling the non-image region and prevent the transfer member from wrapping around the fixing member, however, from the perspective of lowering running cost and improving the glossiness of full color images, there have been attempts to reduce the amount of applied release oil. One such attempt, for example, was a method which included a release agent such as wax or the like in the toner particles, however, in this method a disadvantage arose inasmuch as the toner heat resistance during storage was reduced when the toner particles were made small from the standpoint of high quality images, because it was necessary to include a relatively large amount of wax. Furthermore, the chargeability (i.e., charge rise characteristics and charge stability) of this toner was adversely affected. Particularly in full color image forming apparatuses which consume large amounts of toner an frequently replenish toner, when the charge rise characteristics of the toner is poor, replenished toner cannot be quickly charged to a specific charge amount such that the toner charge become dispersed, and fogging is produced. Furthermore, when low charge toner or reverse charge toner is present due to deterioration of toner chargeability, the carrier and charging member become soiled by the toner component in conjunction with long-term use of the toner, thereby reducing charging performance, and producing dispersion in the amount of charge in the toner, and fogging is produced.
Toner is generally produced by fusion kneading colorant and the like in a binder resin, cooling the material, and thereafter finely pulverizing the material and classifying it to a desired grade. When using a binder resin having a relatively high glass transition point in order to improve heat-resistant storage properties, pulverization efficiency is reduced due to the hardness of the resin, and it is difficult to efficiently produce small toner particles.
It is known that the pulverization property of the toner composition improves when so-called pulverization adjuvant (resin more brittle than the binder resin) is added to the toner composition before kneading. For example, Japanese Laid-Open Patent Application No. H4-257868 discloses art incorporating aromatic petroleum resin C7~C10 in a binding resin such as styrene-butadiene resin and the like, U.S. Pat. No. 5,972,547 discloses art incorporating hydrogenated petroleum resin having a hydrogenation rate of 50% or greater in a binder resin, U.S. Pat. No. 5,972,547 discloses art incorporating a copolymer containing styrene monomer and indene monomer in a binder resin, and U.S. Pat. No. 5,958,642 discloses art incorporating a copolymer containing aliphatic hydrocarbon and aromatic hydrocarbon having nine or more carbon atoms in a binder resin.
In the aforesaid art, however, heat-resistant storage characteristics are reduced and fixing characteristics are reduced. When fixing characteristics are reduced, offset phenomenon (anti-offset) occurs, the transfer member wraps around the fixing member (release characteristics) occur, the image is rubbed by the roller when the sheet bearing the formed image is transported for automatic document feeding or duplex copying, such that image quality is reduced due to bleeding and soiling of the image (smear characteristics). Moreover, in the aforesaid art, although the toner composition is easily pulverized, fine particles, and large particles are easily generated, so as to make it difficult to efficiently produce toner particles of a desired size, which is disadvantageous for toner producibility (yield). The toners obtained by the aforesaid art also large amounts of volatile component that are toxic to humans in the vicinity, and are disadvantageous to safety.
OBJECTS AND SUMMARY
An object of the present invention is to provide a toner for electrostatic latent image developing having excellent fixing characteristics and which is suitable for use in fixing methods, which reduce the amount of applied release oil, or oil-less fixing methods.
Another object of the present invention is to provide a toner for electrostatic latent image developing excellent heat-resistant storage characteristics, safety, chargeability, producibility, and image quality.
The present invention relates to a toner for electrostatic latent image developing incorporating a colorant, binder resin having an number-average molecular weight of 2000 to 5000 and a weight-average molecular weight
umber-average molecular weight ratio of 5 to 30, a polymer having a weight-average molecular weight of 1000~3000 and a weight-average molecular weight
umber-average molecular weight ratio of 2 or less, and a release agent.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The toner particles comprising the toner of the present invention comprise at least a specific polymer (B), release agent, and colorant dispersed in a binder resin (A). Since there is excellent dispersion of the release agent in the toner particles in the toner of the present invention, the toner is suitable for fixing methods using reduced application amounts of release oil, and preferably oil-less fixing methods, such that there is no reduction in the chargeability and heat-resistant storage characteristics, and excellent fixing characteristics (anti-offset, release characteristics, smear characteristics) are ensured.
In the toner of the present invention, it is desirable that the polymer (B) and the release agent be dispersed at average particle size of 1.5 &mgr;m or less, and it is more desirable that the average particle size of the polymer (B) at this time is smaller than the average particle size of the release agent. In a more desirable mode, normally the polymer (B) dispersed in the toner particles of the present invention have an average particle size of 0.05 to 1.0 &mgr;m, desirably 0.08 to 0.8 &mgr;m, and more desirably 0.1 to 0.5 &mgr;m, and the release agent has an average particle size of 0.2 to 1.5 &mgr;m, desirably 0.4 to 1.5 &mgr;m, and more desirably 0.8 to 1.5 &mgr;m, and the average particle size of the polymer (B) is smaller than the average particle size of the release agent. This structure more effectively ensures excellent production characteristics without excessive pulverization when manufacturing the toner. This structure more effectively ensures toner-fixing characteristics (anti-offset, release characteristics, and smear characteristics) in fixing methods using less release oil and more desirably oil-less fixing methods, chargeability, heat-resistant storage characteristics, and flow characteristics. It is believed the isolation of release agent particles from the toner particles due to stress during developing is effectively prevented, and the probability of exposure of release agent on the surface of the toner particles is effectively reduced.
The dispersed particle size of the polymer (B) and the release agent in the toner particles can be measured by the following method. The particle size distribution of the polymer (B) and release agent in the toner is measured by slicing the toner particle using a microtome, staining with osmium stain, photographing the sample magnified 10,000× using a transmission electron microscope (TEM), and subjecting the photographic image to image analysis (Luzex 5000; Nireco Corp.). Differentiation of the polymer (B) and release agent is possible by dispersing polymer (B) and release agent (and colorant and the like if necessary)
Anno Masahiro
Inoue Masahide
Mikuriya Yoahihiro
Burns Doane , Swecker, Mathis LLP
Goodrow John
Minolta Co. , Ltd.
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